How can I solve a far away stacking Freestyle line
I'm not sure if you're already doing this, apologies if so.

You can assign a Distance from Camera modifier to the line thickness in the View Layer Properties tab > Line Style panel.

Before:



After:




You might have to use separate Line Sets for other features whose
detail you want to preserve in the distance.
You can assign the same modifier to Alpha, making the lines more transparent in the distance -  a possible alternative.
As you can see, depending on the resolution of your rendered image, at some thickness, sampling/antialiasing takes over. This might be before your set 0 point; you'll have to tweak the curve / base thickness accordingly.